Capacitive Ultrasonic Transducer and Endo Cavity Ultrasonic Diagnosis System Using the Same

ABSTRACT

A capacitive ultrasonic transducer (c-MUT) comprising a silicon substrate and a transducer element which comprises transducer cells, each of which is constituted by a first electrode equipped on the top surface of the silicon substrate, a second electrode placed opposite to the first electrode with a predetermined gap therefrom and a membrane for supporting the second electrode, wherein a trench is equipped between the adjacent transducers and a conductive film is formed in the trench.

TECHNICAL FIELD

The present invention relates to a capacitive micromachined ultrasonictransducer (c-MUT) produced using silicon process and an endoscopicultrasonic diagnostic system including c-MUT.

BACKGROUND ART

An ultrasonic diagnosis method for transmitting an ultrasound to an endocavity wall and diagnosing by imaging the body tissue using an echosignal from body tissue targets has become widely used. One of theequipment used for the ultrasonic diagnosis method is an ultrasonicendoscope. The ultrasonic endoscope is equipped with an ultrasonictransducer at the head part of an insertion tube which is for insertinginto an endo cavity. The transducer is configured to transmit anultrasound into an endo cavity by converting an electric signal into anultrasound, receive an ultrasound which is reflected from the bodytissue and convert it into an electric signal.

A conventional ultrasonic transducer has been using a ceramic leadzirconate titanate (PZT) as a piezoelectric element for converting anelectric signal into an ultrasound. However, attention is recentlyfocused on a capacitive micromachined ultrasonic transducer (abbreviatedas “c-MUT” hereinafter) produced by processing a silicon semiconductorsubstrate by means of a silicon micromachining technique. This is one ofdevices generally called a micromachine (i.e., Micro Electro-MechanicalSystem: MEMS).

A MEMS device is formed on a silicon substrate or glass substrate as aminiature structure which is an electrically and mechanically combinedcomponent sometimes accompanied with driving integral circuit, such as atransducer for outputting a mechanical force, a driving mechanism fordriving the transducer and a semiconductor integrated circuit forcontrolling the driving mechanism. The basic characteristic of the MEMSdevice lies in integrating the transducer, which is configured as amechanical structure, of a part of the device, and driving thetransducer electrically by applying a Coulomb attraction betweenelectrodes.

Meanwhile, a non-patent document 1 has disclosed a c-MUT as shown inFIG. 1. FIG. 1(a) shows the top face of two sets of a single-dimensionalc-MUT array consisting of 64 pieces of elements; FIG. 1(b) shows asingularized one piece of c-MUT element equipped with dummy neighbors;and FIG. 1(c) shows an enlarged diagram of a c-MUT element structured byparallelly connected by 8×160 pieces of cells.

The c-MUT element 150 comprises a plurality of cells 151, upperelectrodes 152 equipped on the upper parts of individual cells, groundelectrodes 153, dummy neighbors 155 and trenches 156. The upperelectrodes 152 are connected to one another and they are connected tothe electrodes 153 on the ends. The dummy neighbors 155 are forpreventing a crosstalk with the adjacent elements. A trench 156 isequipped between the electrode 153 and dummy neighbor 155.

The upper electrodes are supported by a membrane. Bottom electrodes (notshown herein) are equipped at a position opposite to the upperelectrodes 152 within the cells, and there is a cavity between thebottom electrode and the membrane.

As a voltage is applied to the upper and bottom electrodes of theelement, each cell is simultaneously driven to vibrate concurrently inthe same phase, thereby transmitting an ultrasound.

The non-patent document 1 documents a finding that a Lamb wave (i.e., A0mode) and a Stoneley wave (i.e., a boundary wave) transmitting betweenthe solid phase and fluid phase give a great influence on a crosstalkbetween the elements.

FIG. 2 shows a vibrational wave occurring in a membrane 160 in the caseof generating an ultrasound by using the c-MUT shown in FIG. 1. FIG. 2is a cross-sectional diagram of the element shown in FIG. 1. If thereare distinctive end parts 161 by equipping the trenches 156 on bothends, as in the element 150, a standing wave 162 is generated with theend parts 161 as nodes.

That is, a standing wave is generated between a pair of walls existingapart from each other by a frequency which is determined by the distancebetween the walls and by the transverse sonic velocity of a material(i.e., silicon in the configuration of FIG. 2) filling therebetween.Considering a pair of adjacent trenches, an vibrational wave excited ona membrane is first transmitted along the surface of the membrane as aLamb wave or Stoneley wave. Then an ultrasound, that is the vibrationalwave, is multiply reflected by the right side wall on the left sidetrench and left side wall of the right side trench, becoming possibly atransverse standing wave. The transverse standing wave becomes anvibrational wave with a base having a frequency component of which adistance L is ½λ overlapped with a high-order standing wave of the base.Therefore, the existence of such a pair of walls generates a standingwave. The standing wave 162 is possible to become a noise component inan transducing of an ultrasound.

Non-patent document 1: Xuecheng Jin, et al (3), “Characterization ofOne-Dimensional Capacitive Micromachined Ultrasonic Immersion TransducerArrays”, in “IEEE Transactions on Ultrasonic, Ferroelectrics andFrequency Control”, Vol. 48, NO. 3, P 750-760, May 2001

Non-patent document 2: A. G. Bashford, et al (2), “MicromachinedUltrasonic Capacitance Transducers for Immersion Applications”, in “IEEETransactions on Ultrasonic, Ferroelectrics and Frequency Control”, Vol.45, No. 2, March (1998), P. 367-375

DISCLOSURE OF INVENTION

A capacitive ultrasonic transducer (c-MUT) according to the presentinvention is one comprising a silicon substrate and a transducer elementwhich comprises transducer cells, each of which is constituted by afirst electrode equipped on the top surface of the silicon substrate, asecond electrode placed opposite to the first electrode with apredetermined gap therefrom and a membrane for supporting the secondelectrode, wherein a trench is equipped between the adjacent transducerelements and a conductive film is formed in the trench.

A production method for a c-MUT comprising a silicon substrate and atransducer element which comprises transducer cells, each of which isconstituted by a first electrode equipped on the top surface of thesilicon substrate, a second electrode placed opposite to the firstelectrode with a predetermined gap therefrom and a membrane forsupporting the second electrode according to the present inventioncomprises: a trench forming process for equipping in between theadjacent transducer elements with a trench; and a conductivity formingprocess for forming a third electrode on a bottom of the trench bymaking it conductive.

An endo cavity ultrasonic endoscopic diagnosis system according to thepresent invention comprises: an ultrasonic endoscopic scope equippedwith a c-MUT for transmitting and receiving an ultrasound; a transducerstate discernment unit for discerning such a wrong state of the c-MUT asan electrical short; and an image construction unit for constructing anultrasonic diagnosis image from sensed information sensed by the c-MUTaccording to the state discerned by the transducer state discernmentunit.

An endo cavity ultrasonic endoscopic diagnosis system according to thepresent invention comprises: an ultrasonic endoscope equipped with ac-MUT for transmitting and receiving an ultrasound; a transducer statediscernment unit for discerning a state of the c-MUT; a storage unit forstoring information sensed by the c-MUT; a storage control unit forhaving the storage unit, which corresponds to a discernment result,store the information based on the discernment result by the transducerstate discernment unit; an arithmetic operation unit for performing anarithmetic operation process based on at least one piece of theinformation among the information stored in the storage unit; and animage construction unit for constructing an ultrasonic diagnosis imagefrom an arithmetic operation result of the operation process performedby the arithmetic operation unit.

A noise elimination apparatus for eliminating a noise component frominformation sensed by a c-MUT used for an endo cavity ultrasonicendoscopic diagnosis system comprising an ultrasonic endoscopic scopeequipped with the c-MUT for transmitting and receiving an ultrasoundaccording to the present invention comprises: a first storage unit forstoring the first information sensed by making the c-MUT transmit anultrasound under a condition of the ultrasound not reflecting; a secondstorage unit for storing the second information sensed by the C-MUTtransmitting and receiving an ultrasound under a condition thereof in astate of being in the inside of an endo cavity and yet not touching aninside wall thereof; and an arithmetic operation unit for calculating acorrelation or difference between the second information and firstinformation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a conventional c-MUT;

FIG. 2 is a diagram showing a situation of generating a standing wave ina membrane in the case of using the c-MUT shown in FIG. 1;

FIG. 3 is a diagram showing a radial scanning ultrasonic transduceraccording to a first-1 embodiment;

FIG. 4 is a diagram showing a top view of a single body of a transducerunit according to the first-1 embodiment;

FIG. 5 is a diagram showing a top view of a single body of a transducerelement according to the first-1 embodiment;

FIG. 6 is a diagram of cross-section Aa-Ab of FIG. 5;

FIG. 7A is a diagram showing a production process of a c-MUT accordingto the first-1 embodiment (part 1);

FIG. 7B is a diagram showing a production process of a c-MUT accordingto the first-1 embodiment (part 2);

FIG. 7C is a diagram showing a production process of a c-MUT accordingto the first-1 embodiment (part 3);

FIG. 8 is a diagram exemplifying a variation of a trench form accordingto the first-2 embodiment (part 1);

FIG. 9 is a diagram exemplifying a variation of a trench form accordingto the first-2 embodiment (part 2);

FIG. 10 is a diagram exemplifying a variation of a trench form accordingto the first-2 embodiment (part 3);

FIG. 11 is a diagram exemplifying a variation of a c-MUT elementaccording to the first-3 embodiment (part 1);

FIG. 12 is a diagram exemplifying a variation of a c-MUT elementaccording to the first-3 embodiment (part 2);

FIG. 13 is a diagram exemplifying a variation of a c-MUT elementaccording to the first-3 embodiment (part 3);

FIG. 14 is a diagram exemplifying a variation of a c-MUT elementaccording to the first-3 embodiment (part 4);

FIG. 15 is a diagram exemplifying a variation of a c-MUT elementaccording to the first-3 embodiment (part 5);

FIG. 16A is a diagram exemplifying the case of forming a trench of acurved line when viewing the transducer element according to the first-3embodiment from above;

FIG. 16B is a diagram exemplifying the case of forming a trench of acurved line when viewing the transducer element according to the first-3embodiment from above;

FIG. 16C is a diagram exemplifying the case of forming a trench of acurved line when viewing the transducer element according to the first-3embodiment from above;

FIG. 17 is a diagram showing an outline of an endo cavity ultrasonicdiagnosis system according to a second embodiment;

FIG. 18 is a diagram showing an external configuration of an ultrasonicendoscopic scope according to the present embodiment of the secondembodiment;

FIG. 19 is a diagram showing a comprisal of a capacitive radial andsector scanning array ultrasonic transducer according to the secondembodiment;

FIG. 20 is a diagram showing an ultrasonic anechoic cell according tothe second embodiment;

FIG. 21A is a diagram showing the case of inserting, into an endo cavity(i.e., in the state of inserting into a mouth), an ultrasonic transduceraccording to the second embodiment;

FIG. 21B is a diagram showing the case of inserting, into an endo cavity(i.e., in the states of contacting an ultrasonic transducer with theinside wall of a stomach and transmitting/receiving an ultrasound), anultrasonic transducer according to the second embodiment;

FIG. 22 is a diagram showing an outline of an internal comprisal of anendo cavity ultrasonic diagnosis system according to the secondembodiment;

FIG. 23 is a diagram showing a frequency characteristic when a targetobject is contacting and not contacting with an ultrasonic transduceraccording to a third embodiment;

FIG. 24 is a diagram showing an outline of an internal comprisal of anendo cavity ultrasonic diagnosis system according to the thirdembodiment; and

FIG. 25 is a diagram showing an arithmetic operation control circuit forperforming a signal process of a plurality of patterns according to afourth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

However, the equipment of the trench 156, dummy neighbor 155 andelectrode zone 153 between the trench 156 and cell zone for transmittingand receiving an ultrasound, as in the transducer element 150, makes aratio of the transducer zone to the entirety of the transducer elementsmall.

If the area size of the cell zone is desired to maintain at a certainsize in this case, the transducer element needs to be enlarged,resulting in negating a possibility of miniaturizing an ultrasonictransducer employing the c-MUT. If the size of the element is attemptedto maintain a similar size as before, on the other hand, requiring thearea size of the cell zone to be smaller, resulting in decreasing agenerated output of ultrasounds.

A preferred embodiment of the present invention is to provide a c-MUTnot allowing a decrease of an area size ratio of a cell zone to theentirety of the c-MUT equipped with trenches respectively on both endsof a transducer element, and a reduced output of a generated ultrasound.

Incidentally, if a conventional piezoelectric transducer is operated inthe air, there is a possibility of a breakdown or rapid deterioration ofa characteristic occurring, and therefore an operation in the air hasbeen avoided. This has conventionally limited a use of the ultrasonicendoscopic scope only in the state of contacting with an inside wall ofan endo cavity. Likewise, it is unable to transmit an ultrasound in theair, hence precluding a detection of a noise signal stemming only from atransducer.

Also, a detection of an aerial sonic wave has been conventionallyimpossible by the same structure as a piezoelectric transducer of a typeto be contacting with an endo cavity wall because there is a largedifference in acoustic impedance between a live tissue and air.

Due to this, there has not conventionally been necessary to detectinformation related to a state of an ultrasonic transducer as to whetheror not it contacts with an endo cavity wall.

In the case of using an ultrasonic transducer capable of transmittingand receiving an ultrasound (called as “aerial ultrasound”) in the stateof the ultrasonic transducer not touching with an endo cavity wall,however, a detection of information related to a state of whether or notthe ultrasonic transducer touching an endo cavity wall becomesnecessary.

A preferred embodiment of the present invention accordingly provides anendo cavity ultrasonic diagnosis system which detects informationrelated to a state of whether or not the ultrasonic transducer touchingan endo cavity wall.

Meanwhile, there has conventionally been no endo cavity ultrasonicdiagnosis system existing to obtain an ultrasonic diagnosis image whichis picked up with an ultrasonic transducer touching an endo cavity walland one which is picked up with the transducer not touching the endocavity wall by using the same transducer.

Next, the technique disclosed in the non-patent document 1 equipstrenches respectively on both ends of a transducer element, therebysuppressing a crosstalk between elements, as noted above. The equipmentof such trenches, however, has been faced with the problem of generatinga noise caused by a standing wave when using an element equipped withthe trenches respectively on both ends as described for FIG. 2.

Another preferred embodiment of the present invention accordinglyprovides an endo cavity ultrasonic diagnosis system which builds up anultrasonic diagnosis image related to an asperity of an endo cavity wallwhile inserting, into the endo cavity, an ultrasonic endoscopic scopeequipped with the same c-MUT regardless of it contacting the endo cavitywall, and which also builds up an ultrasonic diagnosis image related toa fault by being stationary held in contact with the endo cavity wallwhen reaching a diagnosis region, with a noise component being removedfrom the thusly buildup ultrasonic diagnosis images.

Now, the following is a description on the preferred embodiment of thepresent invention.

First Embodiment The First-1 Embodiment

The present embodiment describes a production of a transducer elementequipped with a ground electrode on the bottom of a trench.

FIG. 3 shows a capacitive radial scanning array ultrasonic transduceraccording to the present embodiment. The radial scanning ultrasonictransducer 1 comprises a transducer unit 2 constituted by a plurality oftransducer elements 3, by a control circuit unit 4 and by a flexibleprint circuit board (FPC) 5 for interconnection.

A plurality of rectangular transducer units 2 is serially connected in ashort direction thereof, resulting in featuring a cylindrical form. TheFPC 5 is featured with a wiring pattern and electrode pads on the FPC.The control circuit unit 4 is placed, as one control circuit for onetransducer unit, on the reverse side of the c-MUT vis-à-vis the FPC 5and in equi-position with the transducer unit 2. The control circuitunit 4, being equipped on the rear surface of the transducer unit 2(i.e., on the internal circumference of the cylindrical form), isconfigured for controlling an exchange of electrical signals to and fromthe transducer units 2. A through hole penetrating the FPC is featuredfor an element of the c-MUT as unit, and is placed so as to connect thec-MUT unit to control circuit unit via the through hole. The controlcircuit unit 4 is constituted by an integrated circuit such as a pulser,charge amplifier and multiplexer, or by such component. Note that theform of the transducer unit 2 is not limited to a rectangle.

FIG. 4 shows a top view of a single body of the transducer unit 2according to the present embodiment. The transducer unit 2 isconstituted by a plurality of square transducer elements 3. Thetransducer unit 2 shown in FIG. 4 is configured by arraying a pluralityof transducer elements 3 in one dimension. In between the adjacenttransducer units is featured with a trench 7 (i.e., trench formed alongan array direction of transducer unit) penetrating until the FPC 5vertically to the array direction of transducer units. Also, in betweenthe adjacent transducer elements within each transducer unit is featuredwith a trench 6 separating transducer elements of a depth ofapproximately halfway of a silicon substrate 16. Incidentally, a featureof the transducer element is not limited to a square.

FIG. 5 shows a top view of a single body of the transducer element 3according to the present embodiment. The transducer element 3 comprisestrenches 7, trenches 6, interconnection combining transducer electrodes8, 9 and 10, a transducer cell's upper electrode 11, a sacrifice layermaterial removal hole 13 and a through-hole electrode 14 from a bottomelectrode. The back surface (in the direction vertical to the drawing)of the transducer cell's upper electrode 11 is featured with a cavitywhich is indicated as a cavity periphery part 12.

The transducer element 3 is constituted by a plurality of transducercells, of which the number thereof is equal to the number of cavities.FIG. 5 shows a configuration of four transducer cells. The numerical 15shows a dicing line for separating the units.

FIG. 6 is a diagram of cross-section Aa-Ab of FIG. 5. Referring to thecross section, a constituent unit indicated by the numerical 30 iscalled a transducer cell of the transducer element 3 as noted above. Afilm covering the upper part of the transducer cell 30 is called amembrane which is a film constituted by the upper electrode 11, upperlayer 24 above membrane and under layer 22 beneath membrane in theconfiguration shown in FIG. 6. The membrane is an vibrating film fixedby members supporting membrane 20 on both ends of each transducer cell.A bottom electrode 19 is structured on the surface of a siliconsubstrate 16 (at the bottom of a concave part) between the memberssupporting membrane 20 in a manner to be opposite to the upper electrode11, and the bottom electrode 19 is covered over with a dielectric film27 (e.g., SiO₂, Si₃N₄, Ta₂O₅, BaTiO₃, SrTiO₃, AlN and such).

The bottom electrode 19 is equipped with the through-hole electrode 14from bottom electrode for electrically connecting the bottom electrode19 to a electrode pad 26 as signal input-output terminal which isequipped on the bottom face of the silicon substrate 16. Specifically,the bottom electrode 19 is electrically continuous with the electrodepad 26 as signal input-output terminal by way of an interconnection 28featured on the hole surface of the through-hole electrode 14.

The bottom surface of the silicon substrate 16 is covered with a siliconoxide film 17. The upper electrode 11 and interconnection combiningtransducer electrodes 10 are constituted by a metallic film of Au, Al,Pt, Ta, Mo, W or such. The upper electrode 11 is electrically continuouswith a metallic film covering the side and bottom surfaces of thetrenches 6 and 7.

A ground electrode pad 25 is one for making the bottom surface of thesilicon substrate 16 electrically continuous with an electrode featuredon the bottom surface of the trenches 6 and 7 for connecting the upperelectrode 11 to the ground (GND).

The dielectric film 27 is for amplifying a capacitance between the upperelectrode 11 and bottom electrode 19 which sandwich a cavity. Adepletion layer 18 is one in a state of an electron or electron holehardly existing, and there is a case of reducing a capacity possessed bya depletion layer, that is reducing a parasitic capacitance by applyinga reverse bias.

Note that a cavity (i.e., an air gap) 21 is a space surrounded by themembrane, member supporting membrane 20, bottom electrode 19 anddielectric film 27. Incidentally, a sacrifice layer is formed in thecavity in terms of the production process and a under layer beneathmembrane 22 (Si₃N₄) is equipped with a sacrifice layer removal hole 23for removing the sacrifice layer followed by removing the sacrificelayer from the hole when forming the cavity 21.

A “contact resistance” between the ground electrode pad 25 and electrodefeatured on the bottom of the trenches 6 and 7 is configured to beminimally small (i.e., an ohmic contact). The numerical 29 shows adiffusion region.

Describing on an operation of the transducer cell 30, an application ofa voltage to a pair of electrodes of the upper electrode 11 and bottomelectrode 19 makes the electrodes mutually pull each other, followed byreverting back to the original state when reducing the voltage to zero.This movement causes the membrane to vibrate, resulting in generating anultrasound and transmitting it to the upward direction of the upperelectrode 11.

Next is a description of a production process of the c-MUT according tothe present embodiment by referring to FIG. 7 (i.e., FIGS. 7A, 7B and7C).

First, the top surface of an N type silicon substrate 40 (of a thicknessof 100 through 500 micrometers) is masked by an oxide film (SiO₂) 41(step 1). The mask forming forms an oxide film of a thickness of 3000 to4000 angstroms for example by a Wet oxidization method. This is followedby a photolithography process applying a patterning for featuring athrough-hole 42 for through-hole electrode from bottom electrode and byan etching process removing the patterned oxide film.

Next is to apply an Inductively Coupled Plasma-Reactive Ion Etching(ICP-RIE), thereby penetrating a through-hole 42 where it is not maskedin the step 1 (step 2).

Next is to form the depletion layer 43 (step 3). First is to mask thebottom surface of the N type silicon substrate 40 with an oxide film(SiO₂), followed by applying a patterning to the top and bottom surfacesof the N type silicon substrate 40 for forming the depletion layer 43 ina photolithography process and removing the oxide film patterned in theetching process. It is then followed by doping a P type ion (Dope (P+))and applying a heat treatment, thereby forming a P type diffused layer.

The next is to form a contact layer (N+) 44 on both surfaces (step 4).The mask forming process, photolithography process and etching processmask other than a part for forming a contact layer 44 with SiO₂. It isfollowed by doping an N type ion (Dope (N+)) to the unmasked part, andapplying a heat treatment, thereby forming an N type diffusing layer.This is applied to the contact layers (N+) 44 of both surfaces of thesilicon substrate.

The next is to form an electrode film (Pt/Ti) 45 on both surfaces (step5). The first is to remove the mask 41, and mask a part other than thatpart for forming an electrode film with a resist material, followed byforming an electrode film 45 by means of a sputtering and removing theresist material masked in the liftoff process. Note that a material ofthe electrodes may be Au/Cr, Mo, W, phosphor bronze, Al or such, in lieuof being limited to Pt/Ti.

The next is to form a dielectric film (step 6). The dielectric film(e.g., SrTiO₃) 50 is formed by being subjected to the mask formingprocess, sputtering process and liftoff process. Note that thedielectric film 50 may use a material having a high dielectric constant,such as barium titanate BaTiO₃, barium-strontium titanate, tantrumpentoxide, niobium oxide-stabilized tantrum pentoxide, aluminum oxide ortitanium oxide TiO₂, in lieu of the material being limited to SrTiO₃.

The next is to form a layer for supporting membrane (step 7). Theapplication of a mask to apart other than ones for forming the membersupporting membrane is followed by a chemical vapor deposition (CVD)forming an SiN layer and removing the mask, thus resulting in formingthe member supporting membrane formed by the SiN.

The next fills in between the member supporting membrane formed in thestep 7 with a polysilicon 52 as the sacrifice layer (step 8). Note thata material for the sacrifice layer may use a material allowing anetching, such as SiO₂ in lieu of being limited to a material such aspolysilicon which is used for the present embodiment.

The next forms a under layer beneath membrane 22 (step 9). The firststep masks a part becoming a hole 54 for etching out of sacrifice layermaterial and trench 55, followed by the CVD forming an SiN film 53 andremoving the mask. This results in forming the membrane 53 formed by theSiN, the hole 54 and the trench 55.

The next removes the sacrifice layer 52 by means of an etching (step10). Since the present embodiment is configured to use a polysilicon forthe sacrifice layer, the etching is carried out by using XeF₂ as anetching agent for removing the sacrifice layer (of polysilicon) from thehole 54 for etching out of sacrifice layer material. This results informing the cavity 56 and trench 55.

The next closes the hole 54 for etching out of sacrifice layer material(step 11). First masks the bottom (i.e., a contact electrode) of thetrench 55 and forms an SiN film on the entirety of the top surface ofthe element by means of the CVD. It is followed by removing the mask toexpose the bottom (i.e., the contact electrode) of the trench 55.

The last step masks parts other than interconnection combiningtransducer electrodes 8, 9 and 10, transducer cell's upper electrode 11,bottom electrode of the trench 7, and bottom electrode of the trench 6,and forms an electrode film (Pt/Ti) 61 on the entire top face of thetransducer element by subjecting to the sputtering and liftoff (step12), thereby completing the transducer element 3 as shown in FIG. 5.

Note that the forming of the electrode film (and the contact layer),that is, the process for forming the electrode in the trench (i.e., theprocess for making it conductive) is carried out by means of an ionimplantation or CVD and a diffusion process, or a physical vapordeposition (PVD), according to the present embodiment.

As described above, the forming of the ground electrode in the trencheliminates a necessity of equipping a separate zone for a groundelectrode within the transducer element and prevents a reduction of thearea size ratio of an ultrasound output zone to the transducer element.Also, the equipment of the trench enables a suppression of an influenceof a crosstalk between the adjacent elements.

Note that the present embodiment exemplifies a radial type c-MUT; thepresent invention, however, may also be applied to a convex type, lineartype or sector type c-MUT, in lieu of being limited to the presentembodiment.

First-2 Embodiment

Described for the present embodiment is a variation of a form of thetrench featured in a transducer element.

FIG. 8 exemplifies a variation of a trench form according to the presentembodiment (part 1). The numerical 70 and 71 indicate trenches. Thenumerical 76 indicates a silicone substrate. The numerical 72 (i.e., 72a, 72 b and 72 c) indicate contact electrodes on the top face side ofthe silicone substrate 76. The numerical 73 (i.e., 73 a, 73 b and 73 c)indicate contact layers featured in the neighborhood of the contactelectrodes 72 (i.e., 72 a, 72 b and 72 c). The numerical 74 indicates acontact electrode on the lower face side of the silicon substrate 76.The numerical 75 indicates a contact layer featured in the neighborhoodof the contact electrode 74. The numerical 77 and 78 indicate SiNlayers. The numerical 79 indicates an electrode film.

The numerical 70 indicates the case of widening the opening part widerthan the bottom by forming the trench in a taper form. Suchconfiguration enables a use of a sputtering for forming a film on anelectrode. Also enabled is a forming of a thicker film as a result of aneasy attachment of an electrode film by means of a sputtering ascompared to the case of the side face of a trench being perpendicular.This improves a reliability of wiring.

The numerical 71 indicates the case of forming an irregular surface onthe surface of the trench side surface by means of Bosh process. TheBosh process is one for repeating an etching and a passivation (forproviding a surface with protective film so as not to occur a chemicalreaction) processes alternately by using C₄F₈ and SF₆ as reaction gases.It enables a process of a high aspect ratio. In the case of forming atrench by the Bosh process, a change of timing between the passivationand etching makes it possible to form a taper and an irregularity.

A common Bosh process is capable of forming a wavy irregularity in theorder of ones to tens nanometers. The present embodiment, however, isconfigured to form an irregularity of the order of a sub-micrometer onthe side walls for raising the strength of adhesion. This irregularityimproves an adhesiveness of the conductive film connected to the SiN,which is the same material as an invested membrane, and the upperelectrode. It also improves an adhesiveness of a later describedultrasonic attenuation material, leading to an improvement of strengthwhen dicing by a precision dicing.

As such, the forming of surface irregularity on the side surface of thetrench by using the Bosh process enlarges a surface area size and makesan electrode film and SiN film which are invested by the processthereafter hard to come off. Meanwhile, the GND of the contactelectrodes 72 (i.e., 72 a, 72 b and 72 c) existing on the bottom of thetrench is connected to a contact electrode 74 by way of the siliconsubstrate 76.

The trench on the left side of FIG. 8 exemplifies the case of the bottombeing wider than the opening part. As such, the feature of the trenchmay be discretionary.

FIG. 9 exemplifies a variation of a trench form according to the presentembodiment (part 2). FIG. 9 shows the case of cutting the bottom of thetrench deeper into the inside of a silicon substrate 76 than the case ofFIG. 8. This is produced by etching down to the silicon substrate 76,followed by forming a contact layer 73 and filming an electrode with thecontact layer 73 as the base. That is, the forming of the contact layeris followed by forming an SiN film (i.e., closing the hole for removinga sacrifice layer) by means of the CVD and filming a strongcorrosion-resistant electrode member as a base electrode before filmingan electrode 79 which is connected to a membrane so that the contactlayer surface does not have a resistance due to such as naturaloxidization.

As described above, the distance between the contact electrodes 72(i.e., 72 a, 72 b and 72 c) and contact electrode 74 becomes shorter,reducing an electrical loss, thereby improving a reliability of thewiring.

Since a dry etching is employed, it is possible to apply etching in wavyline provided that there is no problem of a mechanical strength. Thatis, a common trench forming (likewise a shearing) is carried out byusing a dicing saw, which is only capable of forming a straight linetrench. However, a dry etching such as ICP-RIE is capable of forming atrench of discretionary form, such as a wavy form.

Meanwhile, if a trench surface is an indeterminate form, a determinateresonance is difficult to occur because lengths are different andtherefore it is beneficial in reducing a crosstalk. Also beneficial isthat it is easy to take out a ground electrode to the back of thesubstrate.

The configuration of having a trench in the silicon substrate provides abenefit of reducing a crosstalk. That is, an ultrasound is transmittedand received by a flexion movement of the membrane, and the flexionmovement allows a generation of crosstalk between the adjacent elementsdue to an vibration such as Lamb wave and Stoneley wave. The flexionmovement transmits a reactionary longitudinal vibrating stress to themember supporting membrane. This vibration reaches at a siliconsubstrate surface from base parts of the member supporting membrane,propagates along the surface of the silicon substrate, and propagatesreversely along the same path to the next neighbor element, thus causinga crosstalk. It is possible to reduce an occurrence of such a crosstalk.

FIG. 10 exemplifies a variation of a trench form according to thepresent embodiment (part 3). FIG. 10 shows the case of joining contactlayers on both faces of a silicon substrate 76. In the case of thesilicon substrate being thin as shown in FIG. 10, or of etching a(GND-use) trench on the silicon substrate, followed by forming contactlayers 73 and 75, diffusing them, and forming the contact layers, thenthe thin contact layers can be mutually connected. This configurationforms a low resistance zone between a contact electrode 72 and contactelectrode 74, making an easy electrical conduction and reducing anelectrical loss, thereby improving a reliability of a wiring.

First-3 Embodiment

Described for the present embodiment is a variation of a c-MUT element.

FIG. 11 is a diagram exemplifying a variation of a c-MUT elementaccording to the present embodiment (part 1).

The numerical 80 indicates a trench. The 86 indicates a siliconsubstrate. The 82 indicates a contact electrode on the upper face sideof the silicon substrate 86. The 83 indicates a contact layer formed inthe neighborhood of the contact electrode 82. The 84 indicates a contactelectrode on the bottom face side of the silicon substrate. The 85indicates a contact layer formed in the neighborhood of the contactelectrode 84. The 87 and 88 indicate SiN layers, respectively. The 89indicates an electrode film. The 90 indicates an SiO₂ film. The 81indicates a through-hole electrode from bottom electrode.

FIG. 11 shows the case of the etching also applied to the surroundingarea of the contact electrode on the bottom face of the siliconsubstrate 86. This configuration is for masking also the bottom surfaceof the silicon substrate with SiO₂ at the stage of the step 1 shown inFIG. 7 and applying the etching to the electrode contact part by meansof a wet etching so as to make it concave form. This configurationfurther shortens the distance between the contact electrodes (82 and 84)on both faces and accordingly reduces an electrical loss and thereforethe reliability of wiring is improved.

Also, the adoption of the configuration of the trench invading thesilicon substrate 86 provides a benefit of reducing a crosstalk as inthe case of FIG. 9. That is, while it transmits and receives anultrasound by the flexion movement of the membrane, the flexion movementgenerates a crosstalk between the adjacent elements due to a Lamb waveor Stoneley wave. The flexion movement transmits a reactionarylongitudinal vibrating stress to the member supporting membrane. Thisvibration reaches at a silicon substrate surface from base parts of themember supporting membrane, propagates along the surface of the siliconsubstrate, and propagates reversely along the same path to the nextneighbor element, thus causing a crosstalk. It is possible to reduce anoccurrence of such a crosstalk by adopting the configuration of thetrench invading the silicon substrate 86. It also provides the benefitof easing an extraction of the ground electrode to the back of thesubstrate.

Note that a Wet oxidization film of SiO₂ may be utilized instead offorming the depletion layer. The reason is that the Wet oxidization filmcan obtain more exact film. Also, it may be possible to apply an N+doping in the trench if it is an N type silicon substrate after formingthe trench and apply a diffusion process by heating, thereby forming acontact layer (N+). Meanwhile, the trench may be such that a part of thebottom is deeper, or that a hole reaches at the bottom face of thesilicon substrate.

FIG. 12 exemplifies a variation of a c-MUT element according to thepresent embodiment (part 2). FIG. 2 shows the case of forming a cavity91 by applying an etching to a silicon substrate 86. In this case, thesilicon substrate 86 also functions as member supporting membrane.

First process applies an anisotropic etching to Si by using TetramethylAmmonium Hydroxide (TMAH). This process forms a cavity 91 and a trench80 of a prescribed depth on the upper face side of the silicon substrate86 and a concave part 95 on the bottom face side thereof.

The next forms a through hole 81 by means of the ICP-RIE. It is followedby filming applying a Wet oxidization for forming an oxide film 90 (usedas a substitute for a depletion layer). Then forms a film of the bottomelectrode 92 (Pt/Ti) to invest the side wall of the through hole 81 witha conductor.

The next forms a film of a dielectrics 93 on the top surface of thebottom electrode 92, followed by applying a heat treatment. Then forms asacrifice layer in the cavity 91 and films an SiN membrane 87 over thesacrifice layer. Then putting a hole 94 in the filmed membrane andremove the sacrifice layer by applying an etching. It is followed byclosing the hole used for a removal of the sacrifice layer by SiN. It isthen covered over with an upper electrode 89.

This process eliminates a necessity of adding a specific process forforming the member supporting membrane, thereby enabling a reduction ofthe number of processes.

FIG. 13 exemplifies a variation of a c-MUT element according to thepresent embodiment (part 3). FIG. 14 exemplifies a variation of a c-MUTelement according to the present embodiment (part 4). FIGS. 13 and 14show the case of filling a trench 80 with a resin 100.

The difference between FIGS. 13 and 14 is either a contact electrode onthe bottom face of a silicon substrate 86 is formed in a concave or not.If the trench 80 is not filled with the resin 100, a transverse standingwave (i.e., an extraneous vibration) may be excited within a transducer,thus unable to obtain a good ultrasonic characteristic. Therefore, thetrench 80 is filled with the resin 100. Its material uses, as anultrasonic attenuation material, a flexible composite resins mixing suchmaterial as a silicone resin, epoxy resin and urethane resin with powderof such material as tungsten fine powder and glass bubble in order toattenuate an vibration caused by an extraneous ultrasound. Thisconfiguration makes it possible to suppress an extraneous vibration.

Incidentally, among the trenches shown in FIGS. 3 through 6 (i.e., thetrenches are featured vertically and horizontally when viewing thetransducer elements from above), the types of transducers having acurved array of the transducers as in the case of the convex and radialtypes are applied by a dicing on at least one side (e.g., the top faceside). If a filled resin exists in such an event, a stress is reduced soas to decrease a peeling, chipping or such of an electrode. Suchdecrease of a chipping as well as an improvement of a reliability of awiring can shorten the distance between the cavity and trench, resultingin increasing a working part from a design view point, thereby leadingto an increased sound pressure per unit area size, that is, an improvedsensitivity and a miniaturization of size.

FIG. 15 exemplifies a variation of a c-MUT element according to thepresent embodiment (part 5). FIG. 15 is a diagram showing the case ofjoining a transducer element to a flexible printed circuit (FPC) byusing a conductive resin 101. Note that an anisotropic conductive film(ACF) or a ball bump made of such material as Au and solder in place ofthe conductive resin 101. Also, an air gap 104 between the FPC and thelower face of the silicon substrate 86 may be filled with a resin.

Also, the trench 80 may be featured with a dicing trench 105 by dicingin place of filling with a resin, or the trench 80 may be filled with aresin followed by featuring a dicing trench 105 by dicing. Or, it may besuch that a forming of a transducer by curving after a dicing, followedby filling with a resin material having a large attenuation. As for adepth of the dicing trench, the dicing must be as deep as reaching theconductive resin 101 if it is a type curving the transducer elementssuch as a convex type and radial type; while a type not curving theelements, such as a linear type, however, al least the siliconesubstrate needs to be diced. Meanwhile, if an electrode 103 of a siliconon the FPC side is formed as concave or hole, a positioning function isobtained and also a mechanical strength of the connection due to anexpansion of an adhering area size, thereby enabling a production of ahighly reliable transducer.

Also, a laser beam may be used for penetrating a silicon substrate. Theuse of the laser beam enables a trench cutting or shearing of adiscretionary form, likewise a dry etching. This obtains a benefit ofreducing a crosstalk, and making a wavy line increases a contact areasize increases, increasing adhesion strength. Also, an ability of makinga form of elements discretionary enables a discretionary cell layout,thereby making it possible to achieve a high density configuration(e.g., an area size ratio of cells to that of an element is large),which is very important for accomplishing a high sensitivity within alimited space such as endoscope.

Incidentally, a trench is commonly straight as shown in FIG. 5 whenviewing a transducer element from above, it is, however, possible toform a curved trench if a photolithography and an etching are applied.FIGS. 16A, 16B and 16C exemplify it.

FIG. 16 (i.e., FIGS. 16A, 16B and 16C) is a diagram exemplifying thecase of forming a trench of a curved line when viewing the transducerelement 3 according to the present embodiment from above. FIG. 16Aexemplifies the case of making trenches 111 (i.e., a horizontal trench111 a and a vertical trench 111 b) surrounding a transducer element 3curved lines and dicing in straight lines (i.e., dicing lines 110). Assuch, all around the transducer element may have a wavy line trench.

FIG. 16B exemplifies the case of making trenches 111 a and 111 bsurrounding a transducer element curved line and dicing in curved lines(i.e., dicing lines 110). It is possible to apply a dicing along thecurved trench by employing a laser dicing.

FIG. 16C exemplifies the case of making a vertical direction trench 111b a straight line and a horizontal direction trench a curved line, amongthe trenches surrounding a transducer element, and dicing in straightlines (i.e., dicing lines 110). The numerical 112 is a ground electrode.As such, it may have a partly wavy line trench structure.

In addition to the examples shown in FIG. 16, a trench form and a dicingform may apparently be a rectangular wave form, saw-tooth wave form, orindeterminate form.

A resonance is stronger and accordingly a standing wave tends to occurin the case of a straight line trench, while extraneous vibrations areweaker as a result of canceling each other in the case of a non-straightline trench. This accordingly reduces a crosstalk, improves an S/N ratioand provides a high image quality image. Note that an adoption of thesame dicing position and ultrasonic attenuation resin as that of astraight line configuration makes it possible to obtain the samefunction and effect.

As described above, the first embodiment is configured to eliminate anecessity of decreasing an area size ratio of a cell zone to theentirety of a c-MUT featured with trenches respectively on both ends ofa transducer element, thereby negating a possibility of reducing anoutput of a generated ultrasound.

Second Embodiment

A description for the present embodiment is on an endo cavity ultrasonicdiagnosis system enabling a noncontact diagnosis by using a radialscanning type c-MUT, in addition to being capable of obtaining atomographic image by being stationary in contact with an endo cavitywall similar to a conventional technique.

FIG. 17 shows an outline of an endo cavity ultrasonic diagnosis systemaccording to the present embodiment. Referring to FIG. 17, the endocavity ultrasonic diagnosis system 201 primarily comprises an ultrasonicendoscopic scope unit 202, a signal process unit 203, an image processunit 205 and a display unit 204. Note that FIG. 17 indicates only areception signal series, while omitting a transmission signal seriesfrom the drawing.

The ultrasonic endoscopic scope unit 202 is equipped with a c-MUT 202-1on the head part thereof. The primary functions of the c-MUT 202-1 isfor first inserting the head part of the ultrasonic endoscopic scopeunit 202 into an endo cavity, transmitting an ultrasound from the c-MUT202-1, receiving an ultrasound reflected within the endo cavity therebyand converting the received ultrasound into an electric signal.

The signal process unit 203 analyzes the electric signal obtained by theultrasonic endoscopic scope unit 202 and performs an arithmeticoperation of it. The signal process unit 203 comprises a storage controlunit 203-1, a storage unit 203-2, an arithmetic operation unit 203-3 anda transducer state discernment unit 203-5.

The transducer state discernment unit 203-5 is configured for discerninga state of the c-MUT, for example, whether the c-MUT 202-1 is on theoutside of a human body or in the inside thereof and not in contact withan endo cavity wall, or in contact therewith. The transducer statediscernment unit 203-5 is constituted by a state detection unit 203-5 aand a detection information discernment unit 203-5 b. The statedetection unit 203-5 a is for detecting a state of the c-MUT 202-1. Thedetection information discernment unit 203-5 b is for discerning a stateof the c-MUT 202-1 based on information detected by the state detectionunit 203-5 a. Note that the transducer state discernment unit 203-5 maybe included in the ultrasonic endoscopic scope unit 202, in the signalprocess unit 203, or in both of them in accordance with the discernmentmethod.

The storage unit 203-2 is for storing sense information (e.g., receivedreflection wave and standing wave) sensed by the c-MUT 202-1. Aplurality of storage units 203-2 exists. Note that a plurality ofphysical storage units or logical zones may exist (i.e., securing aplurality of logical storage zones within a single storage apparatus,with each storage zone being handled as a storage unit).

The storage control unit 203-1 is for storing sense information sensedby the c-MUT 202-1 in a storage unit 203-2 corresponding to adiscernment result based on the discernment result of the transducerstate discernment unit 203-5.

The arithmetic operation unit 203-3 is for performing an arithmeticoperation (e.g., a difference and a correlation function) based on thesense information stored in each storage control unit 203-2. A pluralityof combinations of arithmetic operations exists, enabling the operationin accordance with each purpose.

The image process unit 205 is constituted by an image buildup unit205-1. The image buildup unit 205-1 is for building up an ultrasonicdiagnosis image (e.g., a contour image of an endo cavity wall, an endocavity organization section image, or an image that combines theaforementioned) from the operated signal based on the result of thearithmetic operation at the arithmetic operation unit 203-3.

The display unit 204 is for displaying an ultrasonic diagnosis imagegenerated at the image process unit 205, including a monitor (i.e., adisplay) 204-1 for example. Note that the display unit 204 may be outputequipment such as a printer, in lieu of being limited to a display.

FIG. 18 shows an external configuration of the ultrasonic endoscopicscope 202 according to the present embodiment. The ultrasonic endoscopicscope 202 comprises a control section 209 on the base end of a slenderinsertion tube 212, and a scope connector 211 on one end. From a sidepart of the control section 209 extends a universal cord 210 to beconnected to a light source apparatus (not shown herein). The scopeconnector 211 is further connected to the signal process unit 203.

The insertion tube 212 is constituted by serially connecting, from thehead side, a capacitive radial sector scanning array ultrasonictransducer 206 equipped on the head part, a freely bending section 207,and a flexible tube section 208 having flexibility. The control section209 is equipped with a bending control knob 209 a, enabling a curving ofthe bending section 207 by operating the bending section knob 209 a. Thehead part is also equipped with an illumination lens cover, constitutingan illumination optical part for transmitting an illumination light ontoan observation region, an observation-use lens cover constituting anobservation optical part for capturing an optical image of anobservation region, a forceps exit that is an opening for projecting atreatment instrument, and such, which are not shown herein.

FIG. 19 is a diagram showing a comprisal of a capacitive radial sectorscanning array ultrasonic transducer 206 (named as “ultrasonictransducer”, or “transducer” hereinafter) equipped on the head part ofthe ultrasonic endoscopic scope unit 202 shown in FIG. 18. Theultrasonic transducer 206 is constituted by a two-dimension arraytransducer 220, a transmission/reception circuit 221 and a coaxial cablebundle 222. The two-dimension array transducer 220 is formed by arrayinga plurality of transducer elements. The coaxial cable bundle 222, beinghoused in the insertion tube 212, is made by bundling a plurality ofcables connected to the individual transducer elements. Thetransmission/reception circuit 221 is for controlling signals exchangedwith the transducer elements. That is, the transmission/receptioncircuit 221 is capable of controlling a scanning of a compoundultrasonic beam transmitted from the ultrasonic transducer 206, andcapable of performing not only a radial scan 225 but also a sector scan224 (i.e., an ultrasound sector scanning plane) within a single element(in the cylindrical longitudinal direction). This configuration enablesa buildup of a three-dimensional ultrasonic image. The two-dimensionalarray transducer has been described in detail for FIGS. 3 through 6 ofthe first embodiment, and therefore it is omitted here.

The next description is on a series of flow of operation of the endocavity ultrasonic diagnosis system 201 according to the presentembodiment.

FIG. 20 shows an ultrasonic anechoic cell 270 according to the presentembodiment. A cavity is featured in the inside of the ultrasonicanechoic cell 270, and the ultrasonic transducer 206 is inserted fromthe opening thereof as shown in FIG. 20, followed by transmitting anultrasound. In this event, the ultrasound is not reflected because theultrasonic anechoic cell 270 is structured by a member absorbing theultrasound (e.g., a urethane fiber, a foamed silicone resin or thelike). Therefore, transmitting an ultrasound by an ultrasonic transducerwithin the ultrasonic anechoic cell 270, a reflectance wave is notreceived. Therefore, a charge of the upper electrode does not change atthe time of reception because the membrane basically does not vibrate.In the case of an extraneous vibration such as a standing waveoccurring, however, the charge on the membrane is changed by theinfluence, thus requiring a detection of a change in the charge in thiscase. That is, an extraneous vibration which is not converted into atransmission ultrasound remains as a standing wave associated with anvibration of the membrane at the time of transmission, and the vibrationis overlapped as a noise signal at the time of an actual echo reception,ushering in decreasing an S/N ratio.

FIG. 21 (FIGS. 21A and 21B) show a state of inserting the ultrasonictransducer 206 into an endo cavity, with FIG. 21A showing a state ofinserting it into a mouth and FIG. 21B showing a state of transmittingand receiving an ultrasound by having the ultrasonic transducer 206contact with a stomach wall.

The transmission and reception of an ultrasound is performed in threestates, i.e., the case of performing it in an ultrasonic anechoic cell270 (refer to FIG. 20) (named as “state 1” hereinafter), the case ofperforming it in the air (not in contact with an endo cavity wall)between the insertion into an endo cavity and arrival at an observationregion (refer to FIG. 21A) (named as “state 2” hereinafter) and the caseof performing it with the ultrasonic transducer in contact with an endocavity wall (refer to FIG. 21B) (named as “state 3” hereinafter).

In the case of using a conventional piezoelectric element, it has beenonly possible to obtain an ultrasonic image in the state of the elementin contact with an observation region, whereas a c-MUT, having anacoustic impedance of the ultrasonic transmission/reception face largerthan the air and smaller than a live tissue, thus making it possible toobtain an ultrasonic image in the air (i.e., a state of not in contactwith an endo cavity wall). This makes it possible to easily obtain areflectance wave from an endo cavity wall, enabling a measurement of acontour of a luminal wall, that is, a surface irregularity, whileinserting the ultrasonic transducer. The c-MUT is capable oftransmitting and receiving a high frequency ultrasound of ones MHz, thusenabling a high accuracy detection of a surface irregularity.

FIG. 22 shows an outline of an internal comprisal of an endo cavityultrasonic diagnosis system according to the present embodiment. Theendo cavity ultrasonic diagnosis system is constituted by an ultrasonicendoscopic scope unit 202 and an ultrasonic endoscope diagnosticapparatus 300.

The ultrasonic endoscopic scope unit 202 comprises a c-MUT 301, anoptical sensor 302, a charge amplifier 303 and a pulser (i.e., a pulsegeneration circuit) 304.

The ultrasonic endoscope diagnostic apparatus 300 comprises an signalprocess circuit for optical sensor 305, a switch circuit 306 (includinga selection SW1 for terminals (307), a selection terminal SW2 (308), anda selection terminal SW3 (309)), AD converters 310, 311 and 312, storageapparatuses 313, 314 and 315, arithmetic operation circuits 316, 317 and318, a switch circuit 319 (including a selection terminal Q1 (320), aselection terminal Q2 (321) and a selection terminal (322)), anoperation unit 323, an image converter (i.e., a digital scan converter)324, and a monitor 204-1.

The pulser 304 is a circuit for generating an electric signal fordriving the c-MUT 301.

The charge amplifier 303 comprises the function of performing animpedance conversion (i.e., converting from a high impedance to a lowimpedance), that of detecting a charge on an electrode surface of thec-MUT 301 and that as amplifier. The function of detecting a charge isto detect a charge as a result of the c-MUT 301 receiving a reflectancewave, causing the membrane to vibrate in accordance with the receptionintensity of the reflectance wave and causing a variation of the chargeon the upper electrode in response to the vibration. Note that thepresent embodiment is configured by assuming the case of detecting notonly the charge caused by receiving a reflectance wave but also a chargecaused by an extraneous vibration such as a standing wave. These areincluded in a term “reception signal” in the following description.

The optical sensor 302 is for detecting a brightness of the surroundingarea of the c-MUT 301.

The signal process circuit for optical sensor 305 is for discerning abrightness/darkness based on a signal output from the optical sensor302. That is, it is capable of analyzing a signal based on the lightvolume detected by the optical sensor and discerning a difference ofbrightness in the surrounding of the c-MUT 301.

An example configuration is so as to detect the highest brightness amongthe above described three states in the case of transmitting andreceiving before inserting the ultrasonic transducer 301 into an endocavity, that is, in the ultrasonic anechoic cell 270 (i.e., the state1). Then, a brightness is decreased when inserting the ultrasonictransducer 301 into an endo cavity until reaching at an observationregion (i.e., the state 2), and therefore the configuration is fordetecting the reduced brightness. Then, when the ultrasonic transducerreaches at an observation region (i.e., the state 3), it is configuredto detect reflectance light as a result of the light emitted from thelight guide (not shown herein) equipped in the surrounding of theultrasonic transducer being reflected by the endo cavity wall, andtherefore it is capable of detecting a higher brightness than the state2.

Therefore, the setup of discernment information for the signal processcircuit for optical sensor 305 is such that the ultrasonic transducer301 is judged to be prior to an insertion into an endo cavity (i.e., thestate 1) at an initial state. Then, the brightness decreases from theinsertion into an endo cavity until reaching at an observation region(i.e., the state 2), and therefore the judgment is a state of the state2 if a signal from the optical sensor indicates a value equal to orlower than a threshold value. Then, if the brightness increases and if asignal from the optical sensor indicates a value equal to or higher thanthe threshold value, the ultrasonic transducer is judged to be incontact with an observation region (i.e., the state 3).

The switch circuit 306 is for turning on and off the selection terminalsSW1, SW2 and SW3 in response to an output of the signal process circuitfor optical sensor 305. If the signal process circuit for optical sensor305 judges that the ultrasonic transducer is in a state of being priorto an insertion into an endo cavity (i.e., the state 1), it outputs asignal effecting the state so that the selection SW1 for terminals (307)is turned On as a result of receiving the signal at the switch circuit306. If the signal process circuit for optical sensor 305 judges thatthe ultrasonic transducer is in a state of being inserted into an endocavity and on the move to an observation region (i.e., the state 2), itoutputs a signal effecting the state so that the selection terminal SW2(308) is turned On as a result of receiving the signal at the switchcircuit 306. And, if the signal process circuit for optical sensor 305judges that the ultrasonic transducer is in a state of reaching at anobservation region (i.e., the state 3), it outputs a signal effectingthe state so that the selection terminal SW3 (309) is turned On as aresult of receiving the signal at the switch circuit 306.

A reception signal based on charge information detected at the chargeamplifier 303 is input to either of the AD converter 310, 311 or 312based on the destination of a changeover of the switch circuit 306. TheAD converter 310, 311 or 312 converts the input analog signal into adigital signal. The converted signal is input to either of the storageapparatus 313, 314 or 315, to be stored therein, corresponding to the ADconverter 310, 311 or 312.

The arithmetic operation circuits 316, 317 and 318 calculate acorrelation function among the reception signals (i.e., respectivesignals stored in the storage apparatuses 313, 314 and 315) obtained inthe individual states, thereby making it possible to remove, from therespective reception signals of the states 2 and 3, an extraneousvibrational wave component such as a standing wave that is a noisecomponent obtained in the state 1.

The correlation function includes a cross-correlation function and anautocorrelation function. Explaining the case of using across-correlation function,it is the function of a shift amount of τwhen a waveform of one of two signals is delayed for the τ and isdefined as the following expression: $\begin{matrix}{{{R_{xy}(t)} = {\lim\limits_{T\rightarrow 0}{\frac{1}{T}{\int_{{- T}/2}^{T/2}{{x(t)}{y\left( {t + \tau} \right)}\quad{\mathbb{d}t}}}}}};} & (1)\end{matrix}$

where x(t) is a waveform based on a reception signal in the state of “m”(where an m is discretionary), and y(t) is a waveform based on areception signal in the state of “n” (where an n is discretionary).

The use of the cross-correlation function R_(xy) enables a calculationof similarity between two signals. If the two signals are completelydifferent from each other, the cross-correlation function R_(xy) isclose to zero regardless of a τ. This accordingly makes it possible todetect a component of an extraneous vibration such as a standing waveand accordingly remove the component. Note that a cross-correlationfunction R_(xy) can be obtained by applying an inverse Fourier transformto a cross-spectrum.

Meanwhile, an autocorrelation function can also be used. Theautocorrelation function is a function of a shift amount of τ using awaveform x(t) and a waveform x(t+τ) that is displaced by τ and it isdefined by the following expression: $\begin{matrix}{{R_{xx}(t)} = {\lim\limits_{T\rightarrow 0}{\frac{1}{T}{\int_{{- T}/2}^{T/2}{{x(t)}{x\left( {t + \tau} \right)}\quad{\mathbb{d}t}}}}}} & (2)\end{matrix}$

The autocorrelation function R_(xx) becomes a maximum with τ=0, that is,when it is substituted by a product of itself so that, if a waveform iscyclic, the autocorrelation function indicates peaks in the same cycleas the waveform. If it is an irregular signal and a variation occursslowly, the autocorrelation function indicates a high value where a τ islarge, or if the variation occurs quickly, then the autocorrelationfunction indicates a high value where a τ is small, thus making the τ atemporal indication of a variation. This makes it possible to detect acomponent of an extraneous vibration such as a standing wave, andaccordingly remove the component. Note that an autocorrelation functioncan be obtained by applying an inverse Fourier transform to a powerspectrum.

Note also that another configuration may be so as to remove anextraneous component such as a standing wave by calculating a differencebetween a waveform based on a reception signal in a state of “m” andthat based of a reception signal in a state of “n”, other than themethod of using a correlation function.

Input to the arithmetic operation circuit 316 are a signal stored in thestorage apparatus 313 (i.e., the reception signal in the state 1) and asignal stored in the storage apparatus 314 (i.e., the reception signalin the state 2). The arithmetic operation circuit 316 calculates acorrelation of the two signals or a difference between the two, therebyremoving a component of an extraneous vibration from the receptionsignal in the state 2.

Input to the arithmetic operation circuit 317 are a signal stored in thestorage apparatus 314 (i.e., the reception signal in the state 2) and asignal stored in the storage apparatus 315 (i.e., the reception signalin the state 3). The arithmetic operation circuit 317 likewisecalculates a correlation of the two signals or a difference between thetwo, thereby removing the reception signal in the state 2 from that inthe state 3. This configuration makes it possible to remove also anextraneous vibration component simultaneously.

The arithmetic operation circuit 318 calculates a sum of the signalsobtained by the arithmetic operation circuits 316 and 317. This obtainsa contour image (i.e., surface irregularity information of a luminalwall) and a cross-section image (i.e., information of a depth direction)thereof simultaneously. Note that a correlation of signals obtained atthe arithmetic operation circuits 316 and 317 maybe calculated by usinga correlation function.

The operation unit 323 is for performing a changeover operation of theswitch circuit 319. An operation of the operation unit 323 changes overthe switches included in the switch circuit 319, thereby enabling aselection of an image in a state of a desired output. That is, a signalsubjected to an arithmetic operation at the arithmetic operation circuit316 can be output to the image converter 324 if the selection terminalQ1 (320) is selected. A signal subjected to an arithmetic operation atthe arithmetic operation circuit 318 can be output to the imageconverter 324 if the selection terminal Q2 (321) is selected. And asignal subjected to an arithmetic operation at the arithmetic operationcircuit 317 can be output to the image converter 324 if the selectionterminal Q3 (322) is selected.

A signal prior to being input to the image converter 324 is a time axissignal; it is, however, converted into an image signal by way of theimage converter 324. And thus obtained image signal is output to themonitor 204-1 and an ultrasonic diagnosis image is displayed therein.

As described above, the use of the c-MUT makes it possible to transmitand receive an ultrasound both in the states of the ultrasonictransducer in contact with, and not in contact with, an endo cavitywall, and transmit reception signals of the ultrasound received in therespective states to the respectively corresponding channels.

A “noncontact diagnosis” is enabled in addition to the capability ofobtaining a cross-sectional image by fixing the ultrasonic transducer incontact with an endo cavity wall. The “noncontact diagnosis” makes itpossible to obtain organization feature information of a luminal wall inthe process of inserting the ultrasonic transducer into the endo cavity.That is, an ultrasonic diagnosis which used to be impossible to performby the conventional ultrasonic diagnosis.

Also, performing a signal process for calculating a correlation ordifference between reception signals obtained by the respective statesmakes it possible to remove a standing wave component (i.e., a noisecomponent) that is an extraneous vibration, thereby enabling anobtainment of a clearer ultrasonic diagnosis image than before.

Also, an extraneous vibration component such as a standing wave that isa noise component can be removed from an ultrasonic diagnosis image,thereby enabling an obtainment of a clearer image signal. By this, it ispossible to obtain an ultrasonic diagnosis image that expresses a clearcontour feature of an endo cavity wall even if the ultrasonic diagnosisimage is photographed in a state of the ultrasonic transducer not incontact with the endo cavity wall.

Also, performing a signal process by combining reception signalsobtained in respective states is capable of obtaining a contour image,and an endo cavity cross-section image, of an endo cavity wall.

Also, a use of detection means such as an optical sensor enables adetection of whether or not the ultrasonic transducer contacts with anendo cavity wall and therefore a state of the ultrasonic transducer canbe detected.

Note that the present embodiment is configured to use a radial typec-MUT for obtaining a contour image, and a live organizationcross-section image, of an endo cavity wall; an extraneous vibrationcomponent such as a standing wave, however, can be removed by adopting aconvex type or linear type. Also, the present embodiment is configuredto use an optical sensor for detecting a state of the ultrasonictransducer; the detection of whether or not the ultrasonic transducercontacting with an endo cavity wall, however, is possible by using apressure sensor, for example. And, the present embodiment is configuredto transmit an ultra sound within an ultrasonic anechoic cell forsensing only an extraneous vibration component such as a standing wave;it may be, however, an anechoic environment in which the ultrasound isnot reflected.

Third Embodiment

While the second embodiment is configured to detect whether or not theultrasonic transducer contacts with an endo cavity wall by using anoptical sensor, the present third embodiment describes the case ofdetecting whether or not an ultrasonic transducer contacts with an endocavity wall by a difference of a received ultrasonic frequency.

FIG. 23 is a graph showing a frequency characteristic when a targetobject is contacting or not contacting with an ultrasonic transduceraccording to the present embodiment. The vertical axis of the graphshows a relative amplitude (i.e., values divided by a maximum value ofthem in the vertical axis (i.e., normalized), while the horizontal axisshows frequencies.

The numerical 330 shows a frequency characteristic in a state of theultrasonic transducer not in contact with an object. The 331 shows apeak frequency (fc_non) in a state of the ultrasonic transducer not incontact with an object (i.e., the curve 330). The 332 is a frequencycharacteristic in a state of the ultrasonic transducer in contact withan object. The 333 shows a peak frequency (fc_con) in a state of theultrasonic transducer in contact with an object (i.e., the curve 332).

There is a large difference in the frequency characteristic of theultrasound transmitted between the ultrasonic transducer being incontact and not in contact with an object, that is, an organ wall of theendo cavity according to the graph. The FIG. 20 of the non-patentdocument 2, for example, notes such a change of the frequencycharacteristic between the contact and noncontact. The non-patentdocument 2 notes that a change in a frequency characteristic between thecontact and noncontact is caused by: (1) difference in an acousticimpedance of an acoustic load (i.e., water and air) from the view pointof a membrane, (2) an internal pressure of a cavity located behind themembrane is different due to an acoustic load (i.e., water and air), and(3) a transmission of a high frequency ultrasound into the air isdifficult.

Therefore, a provision of a threshold value between the fc_con andfc_non enables a discernment of which state (i.e., the curve 330 orcurve 332) the ultrasonic transducer is in by using the threshold valueas a border.

FIG. 24 shows an outline of an internal comprisal of an endo cavityultrasonic diagnosis system according to the present embodiment. FIG. 24shows a configuration of removing the optical sensor 302 and signalprocess circuit for optical sensor 305 and adding a low pass filter 325and a wave detector 326 from FIG. 22.

A signal based on charge information detected by the charge amplifier303 is input to the low pass filter 325 which is for passing a signal oflower frequencies than a preset threshold. Therefore, it is possible todiscern that a signal passing the low pass filter is a reception signalin the state of the ultrasonic transducer not contacting with an object,while a signal unable to pass it is a reception signal in the state ofthe ultrasonic transducer contacting with the object.

The wave detector 326 is for detecting a wave of a signal (i.e., analternate current signal) output from the low pass filter 325 andconverting it into a direct current (DC) signal for driving the switchcircuit 306. In the case of an ultrasonic reception signal being a lowfrequency, it passes the low pass filter 325 and the ultrasonicreception signal is input to the wave detector 326 and subjected to anAC/DC conversion. In the case of the ultrasonic reception signal being ahigh frequency, it is cut by the low pass filter 325 and therefore theultrasonic reception signal is not input to the wave detector 326, henceno output therefrom. Meanwhile, a reception signal within the ultrasonicanechoic chamber 270 is not observed other than a low level noise, andtherefore no output comes out of the wave detector 326. Therefore, anoutput from the wave detector 326 is zero at the time of detecting acalibration signal (refer to FIG. 20), is a high level output at thetime of inserting into a lumen (refer to FIG. 21A), and is a low leveloutput at the time of being fixed in contact (refer to FIG. 21B). Theswitches of the switch circuit 306 is changed over from the SW1 (307) toSW2 (308) to SW3 (309) in accordance with the difference of the wavedetection output, and a reception signal in each of the state istransmitted to the AD converters 310, 311 and 312. The operationsthereafter are the same as those of the second embodiment.

By the above operations, the discernment of the difference in frequencycharacteristic makes it possible to detect whether the ultrasonictransducer is on the outside of a human body, or in the inside of anendo cavity and not in contact with an inner wall, or in contacttherewith, thereby enabling a detection of the state of the ultrasonictransducer.

Fourth Embodiment

The present fourth embodiment describes a variation of a signal processbased on an ultrasonic reception signal obtained in each state.

FIG. 25 shows an arithmetic operation control circuit 350 for performinga signal process of a plurality of patterns according to the presentembodiment. The arithmetic operation control circuit 350 is a group ofcircuits corresponding to the arithmetic operation process circuits(316, 317 and 318) and switch circuit 319 which are shown in FIG. 22.

The arithmetic operation control circuit 350 comprises distributors 351,352 and 353, arithmetic operation process circuits 354, 355, 356, 357,358 and 359, and a switch circuit 361. The distributors 351, 352 and 353are for distributing signals output from the respective storageapparatuses 313, 314 and 315 to the respective arithmetic operationprocess circuits. The arithmetic operation process circuits 353 through359 are for calculating a correlation, difference or sum of the inputtwo reception signals.

The second or third embodiments is configured in a manner that a switchcontrol signal 341 output from the signal process circuit for opticalsensor 305 (refer to FIG. 22) or wave detector (refer to FIG. 24) isinput to the switch circuit 306, a switch is changed over based on theinformation of the switch control signal 341.

Then, a signal (i.e., a reception signal 340) based on the chargeinformation detected by the charge amplifier 303 is input to either oneof the AD converter 310, 311 or 312 based on a changeover destination ofthe switch circuit 306. The AD converter 310, 311 or 312 converts theinput analog signal into a digital signal. The converted receptionsignal 340 is input to, and stored in, the storage apparatus 313, 314 or315 corresponding to the converter 310, 311 or 312.

Then, an operator uses the operation unit 323 for selecting as to whichaspect of the reception signal is to be displayed, prompting an outputof a switch control signal 345 from the operation unit 323 to be inputto a switch circuit 361. Either of the selection terminals 361 a, 361 b,361 c, 361 d, 361 e, 361 f, 361 g, 361 h or 361 i is turned On in theswitch circuit 361 based on the switch control signal 345, resulting inoperating an arithmetic operation process circuit connected to theturned-On selection terminal.

Meanwhile, a control signal for memory device 342, 343 or 344 isgenerated based on the signal from the operation unit 323. The storageapparatus 313, receiving the control signal for memory device 342,outputs the stored reception signal (named as “S1” hereinafter) of thestate 1 to the distributor 351. The storage apparatus 314, receiving thecontrol signal for memory device 343, outputs the stored receptionsignal (named as “S2” hereinafter) of the state 2 to the distributor352. The storage apparatus 315, receiving the control signal for memorydevice 344, outputs the stored reception signal (named as “S3”hereinafter) of the state 3 to the distributor 353.

Then, the signal output from each of the storage units 313 through 315is processed by an arithmetic operation by the arithmetic operationprocess circuit, output as an arithmetic operation process signal 346 byway of the switch circuit 361, and input to the image converter 324. Theoperations thereafter are the same as those of the second embodiment.

The next description is on each arithmetic operation in the case of eachof the selection terminals 361 being turned On.

[Case 1] In the case of the selection terminal 361 a being turned On,the signal S1 output from the distributor 351 is output as an arithmeticoperation process signal 346.

[Case 2] In the case of the selection terminal 361 d being turned On,the signal S2 output from the distributor 352 is output as an arithmeticoperation process signal 346.

[Case 3] In the case of the selection terminal 361 i being turned On,the signal S3 output from the distributor 353 is output as an arithmeticoperation process signal 346.

[Case 4] In the case of the selection terminal 361 b being turned On,the signals S1 and S2 output from the distributors 351 and 352 are inputto an arithmetic operation process circuit 354. The arithmetic operationprocess circuit 354 performs an arithmetic operation of S4=S2−S1 forgenerating a signal S4. And the generated signal S4 is output as anarithmetic operation process signal 346.

[Case 5] In the case of the selection terminal 361 f being turned On,the signals S1 and S3 output from the distributors 351 and 353 are inputto an arithmetic operation process circuit 355 which then performs anarithmetic operation of S5=S3−S1 for generating a signal S5. And thegenerated signal S5 is output as an arithmetic operation process signal346.

[Case 6] In the case of the selection terminal 361 h being turned On,the signals S2 and S3 output from the distributors 352 and 353 are inputto an arithmetic operation process circuit 356 which then performs anarithmetic operation of S6=S3−S1 for generating a signal S6. And thegenerated signal S6 is output as an arithmetic operation process signal346.

[Case 7] In the case of the selection terminal 361 c being turned On,the signals S4 and S5 generated at the arithmetic operation processcircuits 354 and 355 are input to an arithmetic operation processcircuit 357 which then performs an arithmetic operation of S7=S4+S5 forgenerating a signal S7. And the generated signal S7 is output as anarithmetic operation process signal 346.

[Case 8] In the case of the selection terminal 361 e being turned On,the signals S5 and S6 generated at the arithmetic operation processcircuits 355 and 366 are input to an arithmetic operation processcircuit 358 which then performs an arithmetic operation of S8=S5+S6 forgenerating a signal S8. And the generated signal S8 is output as anarithmetic operation process signal 346.

[Case 9] In the case of the selection terminal 361 g being turned On,the signals S4 and S6 generated at the arithmetic operation processcircuits 354 and 356 are input to an arithmetic operation processcircuit 359 which then performs an arithmetic operation of S9=S4+S6 forgenerating a signal S9. And the generated signal S9 is output as anarithmetic operation process signal 346.

Each arithmetic operation process is described in detail at this point.The alpha-numerical S1 is noise data related to measurement data (i.e.,a noise or fluctuation stemming from a transducer (including a drivesignal) occurring in association of an ultrasound transmission) at anultrasonic anechoic cell 270 shown in FIG. 20 (i.e., the state 1) forexample, and the noise stemming from the transducer includes a crosstalkvibrational wave related to an in-plane transverse wave propagationunique to the c-MUT and a standing wave.

The S2 is reception ultrasound data in the process of inserting theultrasonic transducer into an endo cavity as shown in FIG. 21A (i.e.,the state 2) and it corresponds to a surface reflection signal from aluminal wall of an endo cavity by using a noncontact aerial ultrasound.This signal also includes a noise signal related to a noise andfluctuation stemming from the transducer. Therefore, the arithmeticoperation of “S4=S2−S1” can remove the noise signal.

Next, the S3 is data including deep diagnosis measurement information inthe case of the transducer fixing and in contact with a luminal wallsurface as shown in FIG. 21B (i.e., the state 3) and it corresponds to adeep reflection signal. This signal includes signal components of the S1and S2. In this case the S1 signal is a noise signal, needing to beremoved and therefore the arithmetic operation and therefore thearithmetic operation of “S5=S3−S1” is performed.

Meanwhile, since the S2 signal includes a noise signal, there is a caseof an arithmetic operation of “S6=S3−S2” being suitable; it results in,however, removing also a surface reflection signal of a luminal wallincluded in the S3 simultaneously. Such a signal process has a shortfallof losing information on an organization of a luminal wall surface of anendo cavity on one hand, while it has an advantage of providing a betterview of a deep diagnosis image as a result of deleting the informationon the organization of the luminal wall surface on the other hand. Assuch, whether using “S5=S3−S1” or “S6=S3−S2” is a discretion of theoperator. This method leads to improving a freedom of diagnosis.

Note that the “S7=S4+S5”, being a result of adding a surface reflectionsignal from a luminal wall with a noise being removed and a deepdiagnosis signal with a noise being removed, enables a uniform diagnosisfrom the surface to deep part. Also the “S8=S5+S6” and “S9=S4+S6” makeit possible to obtain images taking advantage of benefits of therespective signals.

Incidentally, there is a case of the operator being interested inknowing “how the original signal was”, and the capability of detectingby selecting single signals S1, S2 and S3 is provided by the equipmentof the switch circuit 361. Although the present embodiment does notdescribe a signal process after the control signal for memory device 343in detail, it enables a display of a separate window in a monitorscreen, for example, that is a display apparatus.

Also, the present embodiment is configured to calculate the differencebetween the input two signals at the arithmetic operation processcircuits 354, 355 and 356; a correlation function (e.g., across-correlation and an autocorrelation), however, may be used as inthe case of the second embodiment.

Furthermore, the c-MUT is responsive to a Doppler signal control andharmonic imaging, and the ultrasonic diagnosis system of the presentinvention is applicable thereto.

As described above, various pattern of signal process can be carried outbased on an ultrasound reception signal obtained in each state selectedby the operator. This makes it possible to have a generated ultrasonicdiagnosis image comprise a characteristic corresponding to the signalprocess, thereby enabling a multiple aspects of diagnoses.

The present invention eliminates a necessity of decreasing a ratio of anarea size of cell zone to the entirety for a c-MUT featured withtrenches on both ends of an element, thereby eliminating a possibilityof decreasing an output of the ultrasonic transducer.

Also, the present invention enables a transmission and reception of anultrasound in the state of an ultrasonic transducer contacting with anendo cavity wall and not contacting therewith, and also a transmissionof the reception signal of the received ultrasound in each state to acorresponding channel by detecting the state of the ultrasonictransducer.

Moreover, the present invention enables a buildup of an ultrasonicdiagnosis image related to a contour while inserting an ultrasonicendoscopic scope equipped with a same c-MUT regardless of it contactingor not contacting with an endo cavity wall, and also a buildup of anultrasonic diagnosis image related to a cross-sectional image whenreaching at a diagnosis region and being fixed in contact therewith.And, a noise component caused by a standing wave is removed from thethusly buildup ultrasonic diagnosis images.

1. A capacitive ultrasonic transducer (c-MUT) comprising a siliconsubstrate and a transducer element which comprises transducer cells,each of which is constituted by a first electrode equipped on the topsurface of the silicon substrate, a second electrode placed opposite tothe first electrode with a predetermined gap therefrom and a membranefor supporting the second electrode, wherein a trench is equippedbetween the adjacent transducer elements, a conductive film is formed inthe trench, and the c-MUT further comprises a flexible printed circuitboard joined to the back surface of the silicon substrate by way ofelectrode pads placed on the back surface of the silicon substraterespectively for the individual transducer elements.
 2. (canceled) 3.The c-MUT according to claim 1, wherein a bottom of the trench equippedbetween transducer units constituted by the transducer elements, aplurality of which is one-dimensionally arrayed, reaches at a surface ofthe flexible printed circuit by penetrating the silicon substrate andelectrode pad.
 4. The c-MUT according to claim 1, wherein the conductivefilm is formed on a trench interior wall and bottom of the trench andthe conductive film formed on the bottom is joined to an Ohmic contactzone which is featured on the silicon substrate surface.
 5. The c-MUTaccording to claim 1, wherein the trench is filled with an ultrasonicattenuation material.
 6. The c-MUT according to claim 5, wherein theultrasonic attenuation material is a composite resin mixing a finetungsten powder with a resin of which the main component is at leasteither one of epoxy resin, silicone resin, or urethane resin.
 7. Thec-MUT according to claim 1, wherein a cross-sectional form of the trenchis a taper form in which a trench width is decreased with the depth ofthe trench.
 8. The c-MUT according to claim 1, wherein the inside wallof the trench is featured with a surface irregularity of no less than anorder of a sub-micrometer.
 9. The c-MUT according to claim 3, whereinthe penetrating trench surface is covered with the conductive film andis connected to a ground wire equipped on the flexible printed circuitby way of a conductive adhesive, ball bump or anisotropic dielectricsfilm.
 10. The c-MUT according to claim 1, wherein the trench has a curveform or saw-tooth form, at least other than a straight line form whenviewing the transducer element from the above.
 11. A production methodfor a capacitive ultrasonic transducer (c-MUT) comprising a siliconsubstrate and a transducer element which comprises transducer cells,each of which is constituted by a first electrode equipped on the topsurface of the silicon substrate, a second electrode placed opposite tothe first electrode with a predetermined gap therefrom and a membranefor supporting the second electrode, comprising: a trench formingprocess for equipping in between the adjacent transducer elements with atrench; and a conductivity forming process for forming a third electrodeon a bottom of the trench by making it conductive.
 12. The productionmethod for a c-MUT according to claim 11, wherein the conductivityforming process applies an ion implantation or chemical vapor depositionmethod, followed by applying an expansion process, thereby forming thethird electrode.
 13. The production method for a c-MUT according toclaim 11, wherein the conductivity forming process forms the thirdelectrode by a physical vapor deposition.
 14. The production method fora c-MUT according to claim 11, further comprising an ultrasonicattenuation material filling process for filling the trench, in whichthe third electrode is formed, with an ultrasonic attenuation material.15. The production method for a c-MUT according to claim 14, furthercomprising a first cutting process for cutting the trench filled withthe ultrasonic attenuation material.
 16. The production method for ac-MUT according to claim 11, comprising a second cutting process forcutting the trench by cutting through the silicon substrate andelectrode pad and reaching at a surface of the flexible printed circuit.17. The production method for a c-MUT according to claim 15, wherein thefirst cutting process cuts by using a laser beam.
 18. The productionmethod for a c-MUT according to claim 16, wherein the second cuttingprocess cuts by using a laser beam.
 19. An ultrasonic endoscopecomprising the c-MUT according to claim
 1. 20. An endo cavity ultrasonicendoscopic diagnosis system, comprising: an ultrasonic endoscopic scopeequipped with a capacitive ultrasonic transducer (c-MUT) fortransmitting and receiving an ultrasound; a transducer state discernmentunit for discerning a state of the c-MUT; and an image construction unitfor constructing an ultrasonic diagnosis image from sensed informationsensed by the c-MUT according to the state discerned by the transducerstate discernment unit.
 21. The endo cavity ultrasonic endoscopicdiagnosis system according to claim 20, wherein the transducer statediscernment unit comprises a state detection unit for detecting a stateof the c-MUT either of being on the outside of a body and moving withinan endo cavity until reaching an inside wall of the endo cavity, or thatof reaching a target diagnosis region, and a detection informationdiscernment unit for discerning the state based on detection informationobtained from the state detection unit.
 22. The endo cavity ultrasonicendoscopic diagnosis system according to claim 20, further comprising: astorage unit for storing the sensed information, and a storage controlunit for having the storage unit, which corresponds to a discernmentresult, store the sensed information based on the discernment result bythe transducer state discernment unit.
 23. The endo cavity ultrasonicendoscopic diagnosis system according to claim 21, wherein the statedetection unit is an optical sensor equipped approximately in theneighborhood of the c-MUT, and the detection information discernmentunit discerns a state of the c-MUT either of being on the outside of abody, reaching an endo cavity and yet not touching an inside wallthereof, or contacting therewith based on an output of the opticalsensor.
 24. The endo cavity ultrasonic endoscopic diagnosis systemaccording to claim 21, wherein the state detection unit is a pressuresensor equipped approximately in the neighborhood of the c-MUT, and thedetection information discernment unit discerns a state of the c-MUTeither of being on the outside of a body, reaching an endo cavity andyet not touching an inside wall thereof, or contacting therewith basedon an output of the pressure sensor.
 25. The endo cavity ultrasonicendoscopic diagnosis system according to claim 21, wherein the statedetection unit generates the detection information corresponding to anelectric signal expressing the sensed information, and detectioninformation discernment unit discerns a state of the c-MUT either ofbeing on the outside of a body, reaching an endo cavity and yet nottouching an inside wall thereof, or contacting therewith based on thestate detection information.
 26. The endo cavity ultrasonic endoscopicdiagnosis system according to claim 25, wherein a state detection unitis a filter circuit letting the electric signal pass if a frequencythereof is equal to or less than a predefined threshold value.
 27. Anendo cavity ultrasonic endoscopic diagnosis system, comprising: anultrasonic endoscope equipped with a capacitive ultrasonic transducer(c-MUT) for transmitting and receiving an ultrasound; a transducer statediscernment unit for discerning a state of the c-MUT; a storage unit forstoring sensed information sensed by the c-MUT; a storage control unitfor having the storage unit, which corresponds to a discernment result,store the sensed information based on the discernment result by thetransducer state discernment unit; an arithmetic operation unit forperforming an arithmetic operation process based on at least one pieceof the sensed information among the sensed information stored in thestorage unit; and an image construction unit for constructing anultrasonic diagnosis image from an arithmetic operation result of theoperation process performed by the arithmetic operation unit.
 28. Theendo cavity ultrasonic endoscopic diagnosis system according to claim27, wherein the c-MUT is a one-dimensional or two-dimensional array typeC-MUT which is constituted by a plurality of c-MUT elements and whicharrays the plurality thereof on an outer circumference of a cylinder.29. The endo cavity ultrasonic endoscopic diagnosis system according toclaim 28, wherein a trench is featured in between the adjacenttransducer elements.
 30. The endo cavity ultrasonic endoscopic diagnosissystem according to claim 29, wherein a conductive film is formed in thetrench.
 31. The endo cavity ultrasonic endoscopic diagnosis systemaccording to claim 28, further comprising a radial scan control unit formaking a compound ultrasonic beam, which is transmitted from the c-MUT,perform a radial scan along a circumferential direction of the cylinder.32. The endo cavity ultrasonic endoscopic diagnosis system according toclaim 31, wherein the radial scan control unit makes the compoundultrasonic beam perform a sector scan in the longitudinal axis directionof the cylinder.
 33. The endo cavity ultrasonic endoscopic diagnosissystem according to claim 27, wherein the arithmetic operation unitperforms an arithmetic operation for calculating a sum, difference orcorrelation of at least two pieces of the sensed information among thesensed information stored in the storage unit.
 34. The endo cavityultrasonic endoscopic diagnosis system according to claim 27, whereinthe arithmetic operation unit performs an arithmetic operation forcalculating an autocorrelation from one piece of the sensed information.35. The endo cavity ultrasonic endoscopic diagnosis system according toclaim 27, wherein the transducer state discernment unit comprises astate detection unit for detecting a state of the c-MUT either of beingon the outside of a body and moving within an endo cavity until reachingan inside wall of the endo cavity, or that of reaching a targetdiagnosis region, and a detection information discernment unit fordiscerning the state based on detection information obtained from thestate detection unit.
 36. The endo cavity ultrasonic endoscopicdiagnosis system according to claim 35, wherein the state detection unitis an optical sensor equipped approximately in the neighborhood of thec-MUT, and the detection information discernment unit discerns a stateof the c-MUT either of being on the outside of a body, reaching an endocavity and yet not touching an inside wall thereof, or contactingtherewith based on an output of the optical sensor.
 37. The endo cavityultrasonic endoscopic diagnosis system according to claim 35, whereinthe state detection unit is a pressure sensor equipped approximately inthe neighborhood of the c-MUT, and the detection information discernmentunit discerns a state of the c-MUT either of being on the outside of abody, reaching an endo cavity and yet not touching an inside wallthereof, or contacting therewith based on an output of the pressuresensor.
 38. The endo cavity ultrasonic endoscopic diagnosis systemaccording to claim 35, wherein the state detection unit generates thedetection information corresponding to an electric signal expressing thesensed information, and detection information discernment unit discernsa state of the c-MUT either of being on the outside of a body, reachingan endo cavity and yet not touching an inside wall thereof, orcontacting therewith based on the state detection information.
 39. Theendo cavity ultrasonic endoscopic diagnosis system according to claim38, wherein a state detection unit is a filter circuit letting theelectric signal pass if a frequency thereof is equal to or less than apredefined threshold value.
 40. The endo cavity ultrasonic endoscopicdiagnosis system according to claim 27, wherein the storage control unitstores at least one piece of the sensed information among pieces thereofwhich is sensed in a state of the c-MUT either of being on the outsideof a body, reaching an endo cavity and yet not touching an inside wallthereof, or contacting therewith.
 41. The endo cavity ultrasonicendoscopic diagnosis system according to claim 27, wherein the sensedinformation stored in a first storage unit among the storage unit isfirst sensed information sensed by making the c-MUT transmit anultrasound under a condition of the ultrasound not reflecting.
 42. Theendo cavity ultrasonic endoscopic diagnosis system according to claim41, wherein the sensed information stored in a second storage unit amongthe storage unit is second sensed information sensed by the c-MUTtransmitting and receiving an ultrasound in a state of being in an endocavity and yet not touching an inside wall thereof, and the arithmeticoperation unit calculates a correlation or difference between the secondsensed information and first sensed information.
 43. The endo cavityultrasonic endoscopic diagnosis system according to claim 41, whereinthe sensed information stored in a third storage unit among the storageunit is third sensed information sensed by the c-MUT transmitting andreceiving an ultrasound in a state of touching an inside wall of an endocavity, and the arithmetic operation unit calculates a correlation ordifference between the third sensed information and first sensedinformation.
 44. The endo cavity ultrasonic endoscopic diagnosis systemaccording to claim 41, wherein the sensed information stored in a secondstorage unit among the storage unit is second sensed information sensedby the c-MUT transmitting and receiving an ultrasound in a state ofbeing in an endo cavity and yet not touching an inside wall thereof, thesensed information stored in a third storage unit among the storage unitis third sensed information sensed by the c-MUT transmitting andreceiving an ultrasound in a state thereof touching an inside wall of anendo cavity, and the arithmetic operation unit performs a firstarithmetic operation for calculating a correlation or difference betweenthe second sensed information and first sensed information; a secondarithmetic operation for calculating a correlation or difference betweenthe third sensed information and first sensed information; and adds theresults of the first and second arithmetic operations.
 45. The endocavity ultrasonic endoscopic diagnosis system according to claim 42,wherein said ultrasonic diagnosis image is an image expressing a contourof an inside wall surface of an endo cavity.
 46. The endo cavityultrasonic endoscopic diagnosis system according to claim 43, whereinsaid ultrasonic diagnosis image is an image expressing a tomography ofan organization of an endo cavity.
 47. The endo cavity ultrasonicendoscopic diagnosis system according to claim 44, wherein saidultrasonic diagnosis image is an image expressing a contour of an insidewall surface of an endo cavity and one expressing a tomography of anorganization thereof.
 48. A noise elimination apparatus for eliminatinga noise component from sensed information sensed by a capacitiveultrasonic transducer (c-MUT) used for an endo cavity ultrasonicendoscopic diagnosis system comprising an ultrasonic endoscopic scopeequipped with the c-MUT for transmitting and receiving an ultrasound,comprising: a first storage unit for storing the first sensedinformation sensed by making the c-MUT transmit an ultrasound under acondition of the ultrasound not reflecting; a second storage unit forstoring the second sensed information sensed by the c-MUT transmittingand receiving an ultrasound under a condition thereof in a state ofbeing in the inside of an endo cavity and yet not touching an insidewall thereof; and an arithmetic operation unit for calculating acorrelation or difference between the second sensed information andfirst sensed information.
 49. A noise elimination apparatus foreliminating a noise component from sensed information sensed by acapacitive ultrasonic transducer (c-MUT) used for an endo cavityultrasonic endoscopic diagnosis system comprising an ultrasonicendoscopic scope equipped with the c-MUT for transmitting and receivingan ultrasound, comprising: a first storage unit for storing the firstsensed information sensed by making the c-MUT transmit an ultrasoundunder a condition of the ultrasound not reflecting; a third storage unitfor storing the third sensed information sensed by the c-MUTtransmitting and receiving an ultrasound under a condition thereoftouching an inside wall of an endo cavity; and an arithmetic operationunit for calculating a correlation or difference between the thirdsensed information and first sensed information.
 50. A noise eliminationmethod for eliminating a noise component from sensed information sensedby a capacitive ultrasonic transducer (c-MUT) used for an endo cavityultrasonic endoscopic diagnosis system comprising an ultrasonicendoscopic scope equipped with the c-MUT for transmitting and receivingan ultrasound, comprising: obtaining the first sensed information sensedby making the c-MUT transmit an ultrasound under a condition of theultrasound not reflecting; obtaining the second sensed informationsensed by the c-MUT transmitting and receiving an ultrasound under acondition thereof in a state of being in the inside of an endo cavityand yet not touching an inside wall thereof; and calculating acorrelation or difference between the second sensed information andfirst sensed information.
 51. A noise elimination method for eliminatinga noise component from sensed information sensed by a capacitiveultrasonic transducer (c-MUT) used for an endo cavity ultrasonicendoscopic diagnosis system comprising an ultrasonic endoscopic scopeequipped with the c-MUT for transmitting and receiving an ultrasound,comprising: obtaining the first sensed information sensed by making thec-MUT transmit an ultrasound under a condition of the ultrasound notreflecting; obtaining the third sensed information sensed by the c-MUTtransmitting and receiving an ultrasound under a condition thereoftouching an inside wall of an endo cavity; and calculating a correlationor difference between the third sensed information and first sensedinformation.